In many situations, soft tissue must be attached, or re-attached, to bone. By way of example but not limitation, it is common to repair a torn rotator cuff in the shoulder by re-attaching a torn tendon to the humerus. By way of further example but not limitation, it is common to repair a torn labrum in the hip by re-attaching the torn labrum to the acetabulum.
In these and other situations, the soft tissue attachment (or re-attachment) may be effected using a suture anchor. More particularly, a suture anchor, having one or more sutures attached thereto, is mounted to a bone, with the suture(s) being used to attach (or re-attach) the soft tissue to that bone. The suture anchor is typically set into a hole formed in the bone so that the suture anchor is recessed within the bone, with the suture(s) emanating from the bone hole and available to “tie down” soft tissue (e.g., a ligament, labrum, etc.) to the bone.
The suture anchor is sized, shaped and/or otherwise constructed so as to resist withdrawal of the suture anchor from the bone hole, e.g., the suture anchor may comprise screws threads or ribs on its outer surface for gripping the adjacent bone, or the suture anchor may comprise expanding wings for projecting into the side wall of the bone hole, or the suture anchor may be formed in the shape of a wedge so as to lock into the bone, etc.
The suture(s) are generally attached to the suture anchor by passing the suture(s) through an eyelet formed in the proximal end of the suture anchor, although in some cases the suture(s) may be attached to the distal end of the suture anchor or the suture(s) may be attached to an intermediate portion of the suture anchor. In any case, the suture(s) typically extend along the longitudinal axis of the suture anchor as they exit the bone hole. In practice, due to constraints on arthroscopically accessing the repair site, the location of appropriate bone mass for receiving the suture anchor, the disposition of the soft tissue which is to be attached (or re-attached) to the bone, etc., the suture(s) are typically attached to the soft tissue at an angle of between about 0°-50° to the longitudinal axis of the bone hole (i.e., at an angle of between about 0°-50° from the axis along which the suture(s) extend prior to exiting the bone hole).
As noted above, suture anchors generally rely on a friction or interference fit with the surrounding bone in order to resist pull-out of the suture anchor from the bone. Since the loads imposed on the suture anchor may be substantial, and since bone quality may vary from patient to patient, it is generally desirable to increase resistance to pull-out. However, with suture anchors relying on a friction or interference fit with the surrounding bone to resist pull-out, this generally results in the manufacture and use of larger bone anchors. In practice, it is common for “stronger” bone anchors (i.e., bone anchors having greater pull-out strength) to be about 5.0-6.5 mm in diameter, which in turn requires the formation of a bone hole of at least this diameter. This large bone anchor/bone hole configuration displaces a considerable amount of bone at the repair site, particularly where several suture anchors (and hence several bone holes) must be used to effect a repair. At the very least, the use of large suture anchors (and hence the creation of large bone holes) introduces significant trauma for the patient; and in some cases, the need to accommodate such large suture anchors may necessitate the suture anchor being placed dangerously close to an articulating surface of a joint, or to an edge of a bone, etc.
Additionally, in order to maximize the pull-out strength of the suture anchor, many suture anchors employ a construction which “grips” the side wall of the bone hole substantially all the way up to the surface of the bone, e.g., in the case of a screw-type suture anchor, the suture anchor includes screw threads which engage the side wall of the bone hole substantially all the way up to surface of the bone (a so-called “fully-threaded” suture anchor). While such a construction can be highly advantageous since it enables the suture anchor to securely grip against the hard cortical bone which lies near the surface of the bone, it also results in the bone anchor effectively occupying the entire diameter of the bone hole all the way up to the surface of the bone. As a result, the body of the suture anchor acts as something of a dam to impede the flow of bone marrow elements from their origin at the interior of the bone to the site of the soft tissue attachment to the bone. Since these bone marrow elements contain important biological factors which facilitate tendon and bone healing, such “fully-threaded” suture anchors and related devices can significantly impede the healing process.
In addition to the foregoing, the complex mechanical nature of many of the suture anchors requires intricate manufacturing and assembly processes. This drives up suture anchor costs, which in turn drives up the cost of the surgical procedure.
Thus there is a need for a new and improved approach for attaching suture to bone which addresses the deficiencies of the prior art.